This invention relates generally to the manufacture of capsules used to contain medications. More particularly, the present invention relates to a capsule-making machine which incorporates a heating elevator.
Capsules used for the oral administration of pharmaceutical drugs are composed of soluble shells. The shells, which are provided in both "hard" and "soft" forms, are typically composed of gelatin, which is a thermo-gelling material. Gelatin is a tasteless and colorless mixture of derived proteins of the albuminous class which is ordinarily soluble in warm water. Two types of gelatin--Type A and Type B--are commonly used. Type A gelatin is a derivative of acid-treated raw materials. Type B gelatin is a derivative of alkali-treated raw materials.
Capsule shells comprise a cap and a body. The cap partly overlaps the body when the two are attached to form the capsule. A closed container is thereby formed within the capsule for disposition of one or more pharmaceutical drugs.
At present, the manufacture of capsules includes the general steps of gelatin mixing, gelatin warming, formation of the cap and body on pins, the drying of the cap and body, removal of the dried cap and body from the pins, and assembly of the cap and body to form a capsule.
According to the first step, that of gelatin mixing, the gelatin provided in a mixing tank where it is mixed with hot deionized water to melt the gelatin and to bring it to the consistency necessary for capsule formation. Following gelatin warming, the mixed gelatin-water composition is warmed in a transfer tank for the step of gelatin warming.
The mixed and warmed gelatin composition is flowed into a dipping pan. The dipping pan is associated with an apparatus for forming the cap and body. As part of this apparatus, a series of "pin bars" having a series of round-ended and gradually tapered pins extending therefrom is movably provided. The pins are typically composed of stainless steel. Some of the pins are sized so as to form the body portion of the capsule, while a like number of others of the pins are sized so as to form the cap portion of the capsule. It is on the pins of the pin bar that the caps and bodies are formed. The pin bars move, track-like, on the typical capsule-making apparatus from station to station.
One of these stations is provided for pin-dipping. At this station, a number of pin bars are simultaneously caused to be inverted such that the pins of the pin bars are facing downward. The pin bars are then lowered so that the pins are partially immersed into the gelatin. Once immersion is completed, the pin bars are (again simultaneously) elevated and rotated such that the pins are now facing upward.
Following dipping, the partially-coated pin bars are then advanced to a drying station where the gelatin coating is dried by a variety of methods, including kiln drying.
The pin bars having the dried gelatin coating are then advanced to a trimming and removal station. At this point the excess dried gelatin is removed by trimming from each of the caps and bodies and each of these components is then removed from its respective pin. The formed and trimmed caps and bodies are either assembled at an assembly station or are packaged, unassembled, for delivery to the consuming pharmaceutical company.
The development of capsule-making machines goes back at least as early as the 1920's, as evidenced by U.S. Pat. No. 1,787,777, issued on Jan. 6, 1931, to Colton for CAPSULE MACHINE, incorporated by reference herein. This patent teaches the "Colton Machine" which established the standard for the industry.
Additional examples of manufacturing systems for the production of hard capsules for pharmaceutical use are disclosed in U.S. Pat. No. 5,032,074, issued on Jul. 16, 1991, to Muto et al. for APPARATUS FOR MANUFACTURING HARD CAPSULES FOR MEDICAMENT USE and U.S. Pat. No. 5,271,881, issued Dec. 21, 1993, to Redding, Jr., for APPARATUS AND METHOD FOR MAKING MICROCAPSULES. Specific aspects of certain procedures involved in the manufacture of capsules are disclosed in U.S. Pat. No. 4,627,808, issued on Dec. 9, 1986, to Hughes for APPARATUS FOR MAKING CAPSULE HAVING PLURAL CHAMBERS, U.S. Pat. No. 4,636,165, issued on Jan. 13, 1987, to Roast for STRIPPER RINGS FOR CAPSULE PINS, and U.S. Pat. No. 3,842,242, issued on Oct. 15, 1974, to Chisolm for APPARATUS FOR HEATING CAPSULE FORMING PINS. The disclosure of each of the aforementioned references is incorporated by reference herewithin. World Intellectual Property Organization International Publication No. WO 92/21311 for METHOD AND APPARATUS FOR THE MANUFACTURE OF PHARMACEUTICAL CELLULOSE CAPSULES and Canadian Patent No. 1,151,823 for HARD SHELL GELATIN CAPSULE DIPPING APPARATUS AND METHOD show other conventional machines.
The drawback to gelatin capsules is that unmodified gelatin is strongly hydrophilic and is soluble in water. Because of these characteristics, there is a tendency for the gelatin of the capsule to interact with the contained drug. Furthermore, these characteristics represent disadvantages in the handling and storage of gelatin-based capsules.
Recognizing the problems with gelatin-based capsules, efforts have been made to use cellulose as the base for capsule compositions. Specifically, methyl- and ethylcellulose having either alkyl or hydroxyalkyl group substitutions have been used.
While overcoming some of the inherent problems of gelatin-based capsules, cellulose-based capsules present a difficult manufacturing problem. Unlike gelatin-based capsules where the pin bars require no preheating, experience has shown that fluid cellulose-based coatings will flow too freely on an unheated pin. Accordingly, the pin bars must be heated to a point well-above the temperature of ambient air and preferably to approximately 120 degrees Centigrade. This level of heating will assure that the bars are still between 90 and 100 degrees Centigrade by the time the pins are actually dipped into the coating, thus minimizing the flow of the fluid cellulose. This is also necessary in order to provide for the cellulose coating to be properly and uniformly applied.
According to known technology and as mentioned above, a number of pin bars (typically on the order of five) are dipped at one time. Prior to dipping, the pin bars are lined up end-to-end in a heater. As the pin bars are heated, they are delivered to a dipping rack so that a group of pin bars (such as five) may be dipped simultaneously.
As is known, 25 bars per minute are passed through the pin bar heater. In the heater, the pin bars are individually elevated to the requisite temperature at a relatively constant rate of between approximately 2.3 and 2.5 seconds per bar. A run of five bars for the dipping group generates a time gap of between approximately 10.0 and 12.0 seconds between the first bar and the fifth bar.
The problem with the present method of manufacturing pharmaceutical capsules is that it is difficult, perhaps impossible, to maintain all of the bars of the dipping group at a uniform temperature during the critical times of the dipping cycle. Because of the great amount of time necessary to pass the pin bars single-file through the heater, temperature variation between the group of bars to be dipped is between 30 and 60 degrees Centigrade, with the first pin bar out of the heater being considerably cooler than the last pin bar out of the heater. Because it is the temperature of the pin bars which determines the amount of cellulose that will form on the pins (i.e., the warmer the pin bar, the thinner the coating), the present technology limits the production of high-quality cellulose-based capsules having consistent wall thicknesses.
An additional problem with the present method of manufacturing pharmaceutical capsules is one of cap and body removal. Today, it is known to additionally heat the pin bars after kiln drying to allow for easy removal of the cap and body. This is troublesome, as this heating step subjects the material of the capsule to an integrity-damaging procedure which may lead to products of lesser quality than deemed acceptable.
In accordance with the present invention, a preferred embodiment of the capsule-making system is a capsule-making machine which incorporates an elevator at the pre-dipping stage which provides for simultaneous heating of a plurality of pin bars and which allows for their quick movement following heating. The heated elevator station is positioned before the dipping station as part of the capsule-making machine.
In another aspect of the present invention, the elevator comprises a series of vertically stacked braces formed as part of a pin bar rack for receiving and temporarily holding pin bars. In a further aspect of the present invention, a series of hot fluid lines carrying hot fluid such as oil or water are formed within the elevator such that each of the pin bars is evenly heated through radiated heat. In addition, still another aspect of the present invention provides a heater shroud attached to the outer side of the vertical stacks to direct heat to the pin bars from the outside in a controlled manner.
In yet another aspect of the present invention, more than one elevator (i.e., more than one pin bar stack) may be situated in a side-by-side manner. Each elevator preferably accepts twelve stacked pin bars, although a greater or lesser number might be used. An additional aspect of the present invention allows the stack to be selectively moved up or down by means of an arrangement of hydraulic cylinders, the movement of which is managed by a computer. Each cylinder of the multi-cylinder arrangement has a different maximum extension value. By selectively operating each cylinder either at its maximum withdrawn or maximum extended state and by combining cylinder movements, inaccurate movement of the rack is eliminated.
Having the pin bar elevator incorporated therein, the system of the present invention is advantageous over traditional systems for forming pharmaceutical capsules. For example, because the elevator incorporates a single vertical row of pin bars, the internal temperature of the heater unit holding the bars is easier to maintain at a constant level. Furthermore, because each of the pin bars is heated substantially simultaneously, the only time any cooling is allowed to take place is during elevation of the pin bar rack between positions and the ejection of the individual pin bars. The result of this high speed operation is a temperature variation from pin bar to pin bar of only .+-.3 degrees C. An additional advantage of the present invention is that existing capsule making machines (such as the Colton machine or its many variations) may be easily retrofitted to include the pin bar elevator described herein.
Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompany drawings.